Fill each cup with about 1/4 cup yogurt. Place berries, water and sugar in a food processor; pulse until berries are finely chopped. Spoon 1-1/2 tablespoons berry mixture into each cup. Stir gently with a pop stick to swirl.
Top cups with foil; insert pop sticks through foil. Freeze until firm.
For Frozen Clementine & Yogurt Swirls: Substitute 1 cup seeded clementine segments (about 5 medium) and 1/4 cup orange juice for berries, water and sugar; proceed as directed.